The present invention relates to fruit drinks which contain residual sulfur dioxide and/or sodium bisulfite.
Fruit drinks and fruit juice containing products are known to develop an undesirable brown or dark color in a relatively short period of time when exposed to air, due in part at least to oxidative changes. In the absence of air, fruit juices also turn brown but more slowly, apparently from interreaction of juice constituents, to form dark-colored products.
The latter form of browning is a non-enzymic, anaerobic browning. Although sulfur dioxide is used to effectively retard such browning in "air-tight" systems by reacting with reducing sugars, such use is disadvantageous due to sulfur dioxide's characteristic odor and the fact that it eventually gives rise to a unique and unpleasant off-taste described as "skunky", e.g., U.S. Pat. No. 3,219,458.
The former type of browning is from oxidation, such as would be expected to occur in gas permeable containers. It is generally counteracted by several means for reducing atmospheric oxygen to a very low level at the time of packaging. This is accomplished by purging the container with an oxygen-removing gas and thereafter sealing the container. Accordingly, sulfur dioxide and sulfur dioxide producing compounds, e.g., sodium bisulfite, were heretofore believed to find little utility in such fruit drink systems. In fact, U.S. Pat. No. 2,825,651 teaches that sodium bisulfite, in anhydrous form, does not work by itself as an oxygen remover, and in the hydrated form is too active to handle conveniently. This patent teaches that unless copper sulfate pentahydrate is brought into intimate contact with the sulfites either by grinding or by compression into pellets, oxygen removal is ineffective. Also, U.S. Pat. No. 2,628,905 teaches that sodium bisulfite is so acid that solutions of its salts are too unstable, in giving off sulfur dioxide, which is too offensive for treating air exposed slices of fruits and vegetables unless buffered to a pH of from 5.2 to 6.5. One skilled in the art might believe that these limitations apply equally as well to fruit drinks.
Accordingly, a method of packaging fruit drinks which contain sodium bisulfite and residual sulfur dioxide, unbuffered, and uncombined with oxygen-removal compounds, and without extraneous means for reducing atmospheric oxygen at the time of packaging, yet which effectively inhibits oxidative browning while avoiding an offensive odor or taste would be an unexpected and advantageous advancement of the art.